Flotation of potash-containing salts using bivalent, aliphatic alcohols



United States Patent FLOTATION OF POTA'SH-CONTAINING SALTS USING BIVALENT, ALIPHATIC ALCOHOLS Rudolf Baclunann, Hannover, Germany, assignor to Kalivertriebsstelle G. in. b. H., Hannover, Germany (Abt. Kaliforschungsstelle), a corporation of Germany No Drawing. Application June '12, 1952, Serial No. 293,210

Claims priority, application Germany June 26, 1951 8 Claims. (Cl. 209-466) This invention relates to improvements in the flotation of potash-containing salts.

The method of recovering sylvite from crude potash salts by flotation is known. According to the conventional process, the flotation is effected with the use of normal primary amines having more than six carbon atoms as the gathering frother, i. e., the collector. These primary amines generally produce satisfactory results as far as the RC1 yield and the amount of concentrate is concerned. The comsumption of the flotation agents is, however, relatively large, and in many cases so large that the economy of the process is jeopardized, due to the high cost of the amines.

Such a method is described in U. S. Patent No. 2,088,325. In accordance with the method of this patent, for example, about 500 grams of an amine hydrochloride having 12 carbon atoms are required for each ton of the crude salt in the flotation of a sylvinite. It should also be borne in mind that, as the number .of carbon atoms of the amines increases, the consumption alsoincreases.

There are basically two reasons for. this high amine consumption, which is a multiple of the theoretical consumption.

First, the natural, crude potash salts frequently contain amounts of clay or other slime-forming secondary constituents in addition to the salt components. The secondary constituents absorb a large part of the collector which is intended for the flotation of the "salt, and thus prevents its use for this purpose.

Secondly, a part of the amine added is consumed in the formation of the froth.

Attempts were made to overcome these disadvantages by partially removing these secondary constituents before the flotation itself. Such methods are described in U. S. Patents No. 2,288,497 and No. 2,364,520, in which a portion of the clay substances is removed before the crude salt is ground to a fine state. This, however, requires very cumbersome apparatus and a certain K20 loss is inherent in the process itself. Despite this partial removal of the secondary constituents, i. e., the slime,suitable measures must be taken in the flotation process itself to depress the remaining .slime. Inaccordance with U. S. Patent No. 2,288,497, this depression of the remaining slime is effected by the addition of starch. In accordance with U. S. Patent No. 2,364,520, thedepression is effected by the addition of methyl cellulose, cellulose Xanthate, or cellulose acetate. About 300 to 450 grams of starch and about 400 to 800 grams of cellulose derivates are required for each ton of crude salt. These amounts, as can be seen, are extremely high and add considerably to the cost of :the process, thus endangering its economic feasibility.

2,762,509 Patented Sept. 11, 1956 Other attempts to reduce the cost of the process included the use of pine oil for the production of the froth to reduce the amine consumption. These attempts, however, never met with any decisive success.

One object of this invention is the flotation of potashcontaining salts with a reduced consumption of both the flotation amine and of the slime depresser. This, and still further objects, will become apparent from the following description:

It has now been very surprisingly found that the consumption of both the amine and the slime depresser can be very considerably reduced by adding an agent, which is synchronized with the depresser. Put in another way, it may be stated that when using like quantities of amine, it is now very surprisingly possible to obtain greatly increased yields of the desired salts. It has been found, that the frothers, which are known as eflective in flotation, also give good results in combination with amines and appropriate slime depressers, but we have found, that only quite definitely polar-unpolar agents have this substantial improving action.

It was surprisingly found, that the bivalent aliphatic alcohols, having more than 5 carbon atoms, have proven particularly advantageous for this purpose.

The bivalent aliphatic alcohols used in the process of this invention include the alcohols from the hexylglyccl up to the pentadecylglycol. The octylglyco-l has been found particularly successful. The addition of the bivalent aliphatic alcohols may be varied from 1 gram up to grams per ton crude salt. The best results are obtained by an addition of about 25 grams of abivalent aliphatic alcohol per ton crude salt.

' The bivalent aliphatic alcohols may be added at one or more points of the flotation apparatus, but it is preferred to feed the greater part into the first prefrothing cell.

The amounts of the other additional agents such as the amines and the frothers are the same as in known "processes of flotation of potash containing salts.

The complete theoretical reasons for this new startling action have not yet been determined. The method of the improved results will, however, be illustrated by the following examples, which are given solely for this purpose and not limitation.

EXAMPLE I A slime-containing hartsalz was ground to a maximum grain size of 0.4 mm. and floated in its mother liquid without prior slime-removal with the hydrochloride of a normal, primary amine, which consisted essentially of octadecyl amine. IOOgrams of this material were added per ton of the crude salt. The froth concentrate was not refloated. The flotation results as obtained are shown in Table 1 below.

3 EXAMPLE 11 Table 2 [Addition: 150 grams per ton of amine] Weight K01 K61 KC! Yield, Content, Quantity, Yield, percent percent g. percent Concentrate 24. s 71. 2 11. a s1. 5 Tallmgs 75. 1 5. 2 3. 9 18. 5

In both cases, the concentrates had the same KCl content. Upon, however, increasing the amount of amine to 150 grams per ton, the KCl yield rose from 64.1% to 81.5%. A further increase of the yield could only be obtained with very large additional amounts of amine.

EXAMPLE III The same hartsalz was used as in Example I. The salt was prepared in the identical manner. 100 grams per ton of the identical amine were used for the flotation. In addition, 25 grams per ton of cellulose glycolate and 25 grams per ton of octylglycol were added. A substantial increase in the KCl content of the concentrate from 71.3 to 82.6 KCl was obtained. The KCl yield increased from 64.1% in Example I to 89.9%. These results are indicated in Table 3 below.

Table 3 [Addition: 100 grams per ton of amine, 25 grams per ton of cellulose glycolate, 25 grams per ton of octylglycol] Weight K61 K01 K01 Yield, Content, Quantity, Yield, percent percent g. percent Concentrate 22. 5 82. 6 18.6 89. 9 Tailings 77. 5 2. 7 2. 1 10. 1

EXAMPLE IV Table 4 [Additiouz 100 grams per ton of amine, 25 grams per ton of cellulose glycolate, 25 grams per ton of hexylglycol] Weight K01 K01 K01 Yield, Content, Quantity, Yield, percent percent g. percent Concentrate. 22. 5 80. 1 18. 1 88. 4 Tailings 77. 5 3. 1 2. 4 11. 6

EXAMPLE V The same hartsalz Was used as in Example I. The salt was prepared in the identical manner. 100 grams per ton of the identical amine were used for the flotation. In addition 25 grams per ton of cellulose glycolate and 25 grams per ton of tetradecylglycol were added. A great increase in the KCl content of the concentrate up to 79.4% was obtained. The KCl yield increased from 4 64.1% in the Example I to 87.6%. These results are indicated in the Table 5 below.

Table 5 [Additionz grams per ton of amine, 25 grams per ton of cellulose glycolate, 25 grams per ton of tetradecylglycol] All the examples show that the addition of octylglycol in the flotation of potash containing salts results the 0ptimal effects in regard as well with the KCl content of the concentrate as with the KCl yield.

It is thus seen that the slight addition of the bivalent, aliphatic alcohol in accordance with the invention, in addition to the depresser, very startlingly increases the flotation results obtained. With this particularly favorable combination of amines with cellulose glycolates and glycols, a desliming of the crudesalt prior to the flotation is generally no longer necessary. In certain special cases this removal may have afavorable action on the process. In accordance with the invention, the purity of the concentrate and the yield are always substantially improved.

The process is applicable in the same manner to the flotation'of sylvinites, carnallites and all crude salt mixtures, such as are frequently obtained in mining. It is also'applicable to the intermediate and final products obtained in the so-called solution process, the same good results being obtained. The products containing greater amounts of sodium chloride which are obtained on vacuum cooling of hot solutions of sylvinite, hartsalz or carnallite are examples of intermediate products which may be used as starting materials for the process of this invention- I claim:

l. In'the method for the flotation of crude soluble salts in which a suspension of the ground salt in its mother liquid is floated by means of a normal primary amine salt collector with the. addition of a' depressor selected from the group consisting of cellulose derivative depressers and starch product depressers, the improvement which comprises simultaneously adding a bivalent, aliphatic alcohol ranging from hexylglycol to pentadecylglycol, and recovering a concentrate of a high salt content.

2. Improvement according to claim 1, in which said bivalent, aliphatic alcohol is octylglycol.

3. Improvementaccording to claim 1, in which said depresse'r is cellulose glycolate.

4. Improvement according to claim '1, in which said crude salt is selected from the group consisting of sylvinites, hartsalz, carnallites, .and'their mixed salts.

5. Improvement according to claim 1, in which said crude salts are the decomposition products of carnallite.

6. Improvement according to claim 1, in which said crude salts are selected from the group consisting of intermediate and final products of the solution process.

7. Improvement according to claim 1, in which the crude salts are floated with desliming before flotation process.

8. Improvement according to claim 1, in which the crudesalts are floated without desliming before the flotation process.

References Cited in the-file of this patent UNITED STATES PATENTS 

1. IN THE METHOD FOR THE FLOTATION OF CRUDE SOLUBLE SALTS IN WHICH A SUSPENSION OF THE GROUND SALT IN ITS MOTHER LIQUID IS FLOATED BY MEANS OF A NORMAL PRIMARY AMINE SALT COLLECTOR WITH THE ADDITION OF A DEPRESSER SELECTED FROM THE GROUP CONSISTING OF CELLULOSE DERIVATIVE DEPRESSERS AND STARCH PRODUCT DEPRESSERS, THE IMPROVEMENT WHICH COMPRISES SIMULTANEOUSLY ADDING A BIVALENT, ALIPHATIC ALCOHOL RANGING FROM HEXYLGLYCOL TO PENTADECYLGLYCOL, AND RECOVERING A CONCENTRATE OF A HIGH SALT CONTENT. 